/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

#ifndef MEM_H_MODULE
#define MEM_H_MODULE

#if defined(__cplusplus)
extern "C" {
#endif

/*-****************************************
 *  Dependencies
 ******************************************/
#include <stddef.h> /* size_t, ptrdiff_t */
#include <string.h> /* memcpy */

/*-****************************************
 *  Compiler specifics
 ******************************************/
#if defined(_MSC_VER) /* Visual Studio */
#include <stdlib.h>   /* _byteswap_ulong */
#include <intrin.h>   /* _byteswap_* */
#endif
#if defined(__GNUC__)
#define MEM_STATIC static __inline __attribute__((unused))
#elif defined(__cplusplus) || (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
#define MEM_STATIC static inline
#elif defined(_MSC_VER)
#define MEM_STATIC static __inline
#else
#define MEM_STATIC \
  static /* this version may generate warnings for unused static functions; disable the relevant warning */
#endif

#ifndef __has_builtin
#define __has_builtin(x) 0 /* compat. with non-clang compilers */
#endif

/* code only tested on 32 and 64 bits systems */
#define MEM_STATIC_ASSERT(c)                       \
  {                                                \
    enum { MEM_static_assert = 1 / (int)(!!(c)) }; \
  }
MEM_STATIC void MEM_check(void)
{
  MEM_STATIC_ASSERT((sizeof(size_t) == 4) || (sizeof(size_t) == 8));
}

/*-**************************************************************
 *  Basic Types
 *****************************************************************/
#if !defined(__VMS) && (defined(__cplusplus) || (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 \
                                                                                                             */))
#include <stdint.h>
typedef uint8_t BYTE;
typedef uint16_t U16;
typedef int16_t S16;
typedef uint32_t U32;
typedef int32_t S32;
typedef uint64_t U64;
typedef int64_t S64;
#else
#include <limits.h>
#if CHAR_BIT != 8
#error "this implementation requires char to be exactly 8-bit type"
#endif
typedef unsigned char BYTE;
#if USHRT_MAX != 65535
#error "this implementation requires short to be exactly 16-bit type"
#endif
typedef unsigned short U16;
typedef signed short S16;
#if UINT_MAX != 4294967295
#error "this implementation requires int to be exactly 32-bit type"
#endif
typedef unsigned int U32;
typedef signed int S32;
/* note : there are no limits defined for long long type in C90.
 * limits exist in C99, however, in such case, <stdint.h> is preferred */
typedef unsigned long long U64;
typedef signed long long S64;
#endif

/*-**************************************************************
 *  Memory I/O
 *****************************************************************/
/* MEM_FORCE_MEMORY_ACCESS :
 * By default, access to unaligned memory is controlled by `memcpy()`, which is safe and portable.
 * Unfortunately, on some target/compiler combinations, the generated assembly is sub-optimal.
 * The below switch allow to select different access method for improved performance.
 * Method 0 (default) : use `memcpy()`. Safe and portable.
 * Method 1 : `__packed` statement. It depends on compiler extension (i.e., not portable).
 *            This method is safe if your compiler supports it, and *generally* as fast or faster than `memcpy`.
 * Method 2 : direct access. This method is portable but violate C standard.
 *            It can generate buggy code on targets depending on alignment.
 *            In some circumstances, it's the only known way to get the most performance (i.e. GCC + ARMv6)
 * See http://fastcompression.blogspot.fr/2015/08/accessing-unaligned-memory.html for details.
 * Prefer these methods in priority order (0 > 1 > 2)
 */
#ifndef MEM_FORCE_MEMORY_ACCESS /* can be defined externally, on command line for example */
#if defined(__GNUC__) && (defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || \
                             defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_6T2__))
#define MEM_FORCE_MEMORY_ACCESS 2
#elif defined(__INTEL_COMPILER) || defined(__GNUC__)
#define MEM_FORCE_MEMORY_ACCESS 1
#endif
#endif

MEM_STATIC unsigned MEM_32bits(void)
{
  return sizeof(size_t) == 4;
}
MEM_STATIC unsigned MEM_64bits(void)
{
  return sizeof(size_t) == 8;
}

MEM_STATIC unsigned MEM_isLittleEndian(void)
{
  const union {
    U32 u;
    BYTE c[4];
  } one = {1}; /* don't use static : performance detrimental  */
  return one.c[0];
}

#if defined(MEM_FORCE_MEMORY_ACCESS) && (MEM_FORCE_MEMORY_ACCESS == 2)

/* violates C standard, by lying on structure alignment.
Only use if no other choice to achieve best performance on target platform */
MEM_STATIC U16 MEM_read16(const void* memPtr)
{
  return *(const U16*)memPtr;
}
MEM_STATIC U32 MEM_read32(const void* memPtr)
{
  return *(const U32*)memPtr;
}
MEM_STATIC U64 MEM_read64(const void* memPtr)
{
  return *(const U64*)memPtr;
}
MEM_STATIC size_t MEM_readST(const void* memPtr)
{
  return *(const size_t*)memPtr;
}

MEM_STATIC void MEM_write16(void* memPtr, U16 value)
{
  *(U16*)memPtr = value;
}
MEM_STATIC void MEM_write32(void* memPtr, U32 value)
{
  *(U32*)memPtr = value;
}
MEM_STATIC void MEM_write64(void* memPtr, U64 value)
{
  *(U64*)memPtr = value;
}

#elif defined(MEM_FORCE_MEMORY_ACCESS) && (MEM_FORCE_MEMORY_ACCESS == 1)

/* __pack instructions are safer, but compiler specific, hence potentially problematic for some compilers */
/* currently only defined for gcc and icc */
#if defined(_MSC_VER) || (defined(__INTEL_COMPILER) && defined(WIN32))
__pragma(pack(push, 1)) typedef struct {
  U16 v;
} unalign16;
typedef struct {
  U32 v;
} unalign32;
typedef struct {
  U64 v;
} unalign64;
typedef struct {
  size_t v;
} unalignArch;
__pragma(pack(pop))
#else
typedef struct {
  U16 v;
} __attribute__((packed)) unalign16;
typedef struct {
  U32 v;
} __attribute__((packed)) unalign32;
typedef struct {
  U64 v;
} __attribute__((packed)) unalign64;
typedef struct {
  size_t v;
} __attribute__((packed)) unalignArch;
#endif

    MEM_STATIC U16 MEM_read16(const void* ptr)
{
  return ((const unalign16*)ptr)->v;
}
MEM_STATIC U32 MEM_read32(const void* ptr)
{
  return ((const unalign32*)ptr)->v;
}
MEM_STATIC U64 MEM_read64(const void* ptr)
{
  return ((const unalign64*)ptr)->v;
}
MEM_STATIC size_t MEM_readST(const void* ptr)
{
  return ((const unalignArch*)ptr)->v;
}

MEM_STATIC void MEM_write16(void* memPtr, U16 value)
{
  ((unalign16*)memPtr)->v = value;
}
MEM_STATIC void MEM_write32(void* memPtr, U32 value)
{
  ((unalign32*)memPtr)->v = value;
}
MEM_STATIC void MEM_write64(void* memPtr, U64 value)
{
  ((unalign64*)memPtr)->v = value;
}

#else

/* default method, safe and standard.
   can sometimes prove slower */

MEM_STATIC U16 MEM_read16(const void* memPtr)
{
  U16 val;
  memcpy(&val, memPtr, sizeof(val));
  return val;
}

MEM_STATIC U32 MEM_read32(const void* memPtr)
{
  U32 val;
  memcpy(&val, memPtr, sizeof(val));
  return val;
}

MEM_STATIC U64 MEM_read64(const void* memPtr)
{
  U64 val;
  memcpy(&val, memPtr, sizeof(val));
  return val;
}

MEM_STATIC size_t MEM_readST(const void* memPtr)
{
  size_t val;
  memcpy(&val, memPtr, sizeof(val));
  return val;
}

MEM_STATIC void MEM_write16(void* memPtr, U16 value)
{
  memcpy(memPtr, &value, sizeof(value));
}

MEM_STATIC void MEM_write32(void* memPtr, U32 value)
{
  memcpy(memPtr, &value, sizeof(value));
}

MEM_STATIC void MEM_write64(void* memPtr, U64 value)
{
  memcpy(memPtr, &value, sizeof(value));
}

#endif /* MEM_FORCE_MEMORY_ACCESS */

MEM_STATIC U32 MEM_swap32(U32 in)
{
#if defined(_MSC_VER) /* Visual Studio */
  return _byteswap_ulong(in);
#elif (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 403)) || \
    (defined(__clang__) && __has_builtin(__builtin_bswap32))
  return __builtin_bswap32(in);
#else
  return ((in << 24) & 0xff000000) | ((in << 8) & 0x00ff0000) | ((in >> 8) & 0x0000ff00) | ((in >> 24) & 0x000000ff);
#endif
}

MEM_STATIC U64 MEM_swap64(U64 in)
{
#if defined(_MSC_VER) /* Visual Studio */
  return _byteswap_uint64(in);
#elif (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 403)) || \
    (defined(__clang__) && __has_builtin(__builtin_bswap64))
  return __builtin_bswap64(in);
#else
  return ((in << 56) & 0xff00000000000000ULL) | ((in << 40) & 0x00ff000000000000ULL) |
         ((in << 24) & 0x0000ff0000000000ULL) | ((in << 8) & 0x000000ff00000000ULL) |
         ((in >> 8) & 0x00000000ff000000ULL) | ((in >> 24) & 0x0000000000ff0000ULL) |
         ((in >> 40) & 0x000000000000ff00ULL) | ((in >> 56) & 0x00000000000000ffULL);
#endif
}

MEM_STATIC size_t MEM_swapST(size_t in)
{
  if (MEM_32bits())
    return (size_t)MEM_swap32((U32)in);
  else
    return (size_t)MEM_swap64((U64)in);
}

/*=== Little endian r/w ===*/

MEM_STATIC U16 MEM_readLE16(const void* memPtr)
{
  if (MEM_isLittleEndian())
    return MEM_read16(memPtr);
  else {
    const BYTE* p = (const BYTE*)memPtr;
    return (U16)(p[0] + (p[1] << 8));
  }
}

MEM_STATIC void MEM_writeLE16(void* memPtr, U16 val)
{
  if (MEM_isLittleEndian()) {
    MEM_write16(memPtr, val);
  } else {
    BYTE* p = (BYTE*)memPtr;
    p[0] = (BYTE)val;
    p[1] = (BYTE)(val >> 8);
  }
}

MEM_STATIC U32 MEM_readLE24(const void* memPtr)
{
  return MEM_readLE16(memPtr) + (((const BYTE*)memPtr)[2] << 16);
}

MEM_STATIC void MEM_writeLE24(void* memPtr, U32 val)
{
  MEM_writeLE16(memPtr, (U16)val);
  ((BYTE*)memPtr)[2] = (BYTE)(val >> 16);
}

MEM_STATIC U32 MEM_readLE32(const void* memPtr)
{
  if (MEM_isLittleEndian())
    return MEM_read32(memPtr);
  else
    return MEM_swap32(MEM_read32(memPtr));
}

MEM_STATIC void MEM_writeLE32(void* memPtr, U32 val32)
{
  if (MEM_isLittleEndian())
    MEM_write32(memPtr, val32);
  else
    MEM_write32(memPtr, MEM_swap32(val32));
}

MEM_STATIC U64 MEM_readLE64(const void* memPtr)
{
  if (MEM_isLittleEndian())
    return MEM_read64(memPtr);
  else
    return MEM_swap64(MEM_read64(memPtr));
}

MEM_STATIC void MEM_writeLE64(void* memPtr, U64 val64)
{
  if (MEM_isLittleEndian())
    MEM_write64(memPtr, val64);
  else
    MEM_write64(memPtr, MEM_swap64(val64));
}

MEM_STATIC size_t MEM_readLEST(const void* memPtr)
{
  if (MEM_32bits())
    return (size_t)MEM_readLE32(memPtr);
  else
    return (size_t)MEM_readLE64(memPtr);
}

MEM_STATIC void MEM_writeLEST(void* memPtr, size_t val)
{
  if (MEM_32bits())
    MEM_writeLE32(memPtr, (U32)val);
  else
    MEM_writeLE64(memPtr, (U64)val);
}

/*=== Big endian r/w ===*/

MEM_STATIC U32 MEM_readBE32(const void* memPtr)
{
  if (MEM_isLittleEndian())
    return MEM_swap32(MEM_read32(memPtr));
  else
    return MEM_read32(memPtr);
}

MEM_STATIC void MEM_writeBE32(void* memPtr, U32 val32)
{
  if (MEM_isLittleEndian())
    MEM_write32(memPtr, MEM_swap32(val32));
  else
    MEM_write32(memPtr, val32);
}

MEM_STATIC U64 MEM_readBE64(const void* memPtr)
{
  if (MEM_isLittleEndian())
    return MEM_swap64(MEM_read64(memPtr));
  else
    return MEM_read64(memPtr);
}

MEM_STATIC void MEM_writeBE64(void* memPtr, U64 val64)
{
  if (MEM_isLittleEndian())
    MEM_write64(memPtr, MEM_swap64(val64));
  else
    MEM_write64(memPtr, val64);
}

MEM_STATIC size_t MEM_readBEST(const void* memPtr)
{
  if (MEM_32bits())
    return (size_t)MEM_readBE32(memPtr);
  else
    return (size_t)MEM_readBE64(memPtr);
}

MEM_STATIC void MEM_writeBEST(void* memPtr, size_t val)
{
  if (MEM_32bits())
    MEM_writeBE32(memPtr, (U32)val);
  else
    MEM_writeBE64(memPtr, (U64)val);
}

#if defined(__cplusplus)
}
#endif

#endif /* MEM_H_MODULE */
